1. Field of the Invention
This invention relates to a partially reflect surface antenna, and more particularly to a partially reflect surface antenna capable of increasing aperture efficiency and reducing manufacturing cost of the micro-strip reflective unit of the reflective sheet.
2. Description of Related Art
In the recent years, due to the conventional partially reflective surface antenna with low profile can be made by the print circuit board, and therefore it is widely used in the military or civil industry. However, the aperture efficiency of the conventional partially reflective surface antenna is also limited.
FIG. 1 is a schematic view illustrating a conventional partially reflective surface antenna, wherein the partially reflective surface antenna comprises a substrate 11, a reflective sheet 12, and a plurality of supporting units 131, 132, 133, 134. The substrate 11 and the reflective sheet 12 each is an FR-4 microwave substrate with the thickness of 0.8 mm, and each supporting unit maintains a predetermined distance between the substrate 11 and the reflective sheet 12. Further, the substrate 11 has an upper surface 111 with a signal I/O portion 112 electrically connected to a coaxial cable 113 for receiving or outputting a high frequency signal.
Referring to FIG. 1, an array antenna block 14 locates at the center of the surface of the reflective sheet 12, and the area of the array antenna block 14 is substantially equal to the surface area of the reflective sheet 12. In addition, an antenna array 141 locates inside the array antenna block 14, and the antenna array 141 comprises one hundred and twenty one micro-strip reflective units 142 for forming as an 11×11 array.
In addition, in conventional partially reflective antenna, the reflective sheet 12 is a square-shaped plate with a dimension of 12.9 cm×12.9 cm, and the array antenna block 14 is a square-shaped with a dimension of 12 cm×12 cm. The micro-strip reflective unit 142 composes antenna array 141 of the array antenna block that is formed in a square shape with a dimension of 1 cm×1 cm. In antenna array 141, the distance (Dx1) in the direction of X and the distance (Dy1) in the direction of Y between the two micro-strip reflective units 142 respectively is 1 mm.
The conventional partially reflective antenna can substantially adjust the arrangement of the micro-strip reflective unit 142 for increasing the direction of the high frequency signal. However, the conventional partially reflective antenna only uses metal material to reflect the electrical wave without considering using other material such as insulating material to reflect the electrical wave. Therefore, the conventional partially reflective antenna will cost lots of metal material to manufacture the micro-strip reflective unit and fill them up to the reflective sheet. Also, the conventional partially reflective antenna is unable to use non-metal material to increase the aperture efficiency of the high frequency signal.
Therefore, it is desirable for the industries to provide a partially reflective antenna, which not only can reduce the manufacture cost of the micro-strip reflective unit, but also can increase the aperture efficiency.